This invention relates to reinforcement of a hollow structure, and more particularly, the invention relates to reinforcing a hollow structure with a material such as a structural foam.
Hollow structural members are used in a variety of vehicle applications. For example, portions of the vehicle body such as A- and B-pillars are formed from thin-walled hollow members. Also, suspension assemblies are incorporating increasingly thinner walls for tubular members such as axles. Utilizing thin walled structural members has the advantage of reducing the cost and weight of the assembly incorporating the structure.
In the case of axles, it is desirable to provide a wall thickness that maximizes bending and torsional stiffness while minimizing the weight. However, the thinner the wall thickness, the more susceptible the structure is to buckling under load. For example, auxiliary hardware such as spring brackets are typically clamped to the hollow axle structure. The wall may buckle under the clamping load or the leaf spring may walk during operation of the suspension assembly. To this end, prior art axle assemblies have added local stiffeners such as by welding on additional reinforcement plates to increase the stiffness.
For vehicle applications such as hollow body structures, such as A- and B-pillars, structural foams have been injected into the hollow cavity of the structure to provide localized reinforcement. The structural foam expands to fill the space and hardens to stiffen the area. However, walls must be formed in the hollow structure to contain the foam to the desired area since the structural foam is very costly. This is accomplished by stamping or welding steel walls into the structure to contain the foam. This raises complications in forming the hollow structural member which can add significant cost when formulating a design to accommodate the walls for containing the structural foam.
Therefore, what is needed is a method and apparatus for providing local reinforcement of a hollow structural member while reducing the cost and design complexity of prior art solutions.